The present invention is designed to combine the compression generation of a cross-screw with the bending and torsional strength of a plate. Thus, the present invention offers a unique and versatile plating option for fixation and stabilization such as for fusion surgeries for various bones in the lower leg and arm. These plates feature a contouring intended to fit a variety of anatomic sites, while creating a low-profile construct and reducing the need for intra-operative plate bending. The invention is applicable as well to application specific plates which are designed for a particular anatomical location and surgical purpose.
These plates feature multiple compression housings or “pockets”, which each accepts an obliquely extending screw. This allows a surgeon the option to compress across a fracture or bone interface with a first pocket screw, then gain additional targeted inter-fragmentary fixation using a second pocket screw. Both pockets are designed to provide targeted insertion of suitable screw, such as a 4.0 mm inter-fragmentary screw, through the plate and across the joint or fracture line. The plate is designed to allow for multi-planar fixation with a set of inwardly angled (relative to the plate midpoint) screws and a set of more traditionally placed locking screws (or variably angled locking screws) that help to hold the plate relative to the bones. The present design is meant to reduce the risk of hardware collision associated with supplementary cross-screw insertion outside of a plate. In accordance with the invention, these plates are not right- or left-side specific, but are offered in Alpha™ and Beta™ versions (which are mirror images), designating pocket position and direction of compression. The plates in accordance with the invention are provided in a set or “surgical tray or caddy” which includes specialty instrumentation such as a countersink having a compound opening, which accommodates the underside compression pocket as the pocket screw is inserted and compression is achieved. Thus, these instruments aid in simple and accurate plate and screw insertion. In addition, the plates of the invention generally include threaded screw holes as the usual screw holes which accommodate either non-locking, fixed-angle locking and variable-angle locking screws for selective fixation without compromise of the mechanical properties of the type of fixation.
The present invention combines the advantages of the prior art screw/pin fusion methods with the advantages of a plate, and allows the surgeon the option of using multiple inter-fragmentary or fusion compression screws in a procedure that also incorporates a plate and thus provides the advantages of stress shielding and force loading or balancing that permits earlier weight bearing. Templates are provided which facilitate the operative procedure, including alignment which can remain in position during placement of the plate, counter-boring the surgical site to accommodate the compression screw housings and placement of the “inter-fragmentary” or compression screws. Further, the plate includes elongated wire and/or screw holes that allow for the compression and attendant relative bone movement during the surgery by the engagement of the compression screw. The compression screw or screws are placed in the plate so as to minimize the possibility of interference with the guide wires and traditional plate screws. The openings in the plate for the compression screws are provided so as to allow for opposing inter-fragmentary screws. They generally are offset from each other along the long direction of the plate. This allows a placement of a compression screw that exerts a force on a diagonal to the long axis of the plate (i.e. a compound force relative to the plate having a greater horizontal force component than is traditionally used to hold a plate relative to the bone). Further, these compression housings or “pockets” are provided so as to project below the bone-facing surface of the plate where the pockets provide a closed or sheltered screw/plate interface and the external surface of the pockets can also bear against the bone to help provide a compressive force. The pockets include a slotted opening for the compression screw. Thus, the screw can be angled with a single degree of freedom (i.e. linearly) with respect to the axis of the compression screw hole in the housing.
When proper technique is followed, the first pocket screw will generate compression across the joint. As is the case with any pocket plate, the plate must first be fixed on the same side of the joint as the pocket screw. As the first pocket screw is inserted, the bone will translate (compress) towards the unfixed aspect of the joint. In order for the plate to remain flush against the bone during compression, the empty pocket (or second pocket) must have space to slide within the prepared bone. The instruments provided are used to “over-countersink” for the second pocket screw, which allows the plate to translate within an over-sized bore, while maintaining a low-profile fit on the bone.